Repurpose Old Bakelite Valve Radio Unit

[Ohkie]

Hi All,

First post here and after some advice and guidance. Forgive me if there is a better forum to post in.

I've come into possession of an old Bakelite radio enclosure (see here for reference: http://ronebergcairns.com/2008onwards/general2008_4035.jpg ). It's a Tecnico Aristocrat 651 manufactured in Australia.

It's an old valve radio from the 40/50s, and the internals are all missing except for the base where everything was mounted to.

I picked it up because I liked the idea of repurposing the unit with a touchscreen and new speaker as a background audio device for our main living area.

I intend to use my programming background to write the code and interface to google music or a similar online radio source using a raspberry pi and touchscreen. I also intend to hook up the old dials to the computer so that will be a learning experience on its own.

But I've realised I'm totally out of my depth with the actual hardware side and thats why I'm here.

The unit looks to have originally had a single 8 inch speaker, and I've discovered that decent and cheap mono amplifiers are not that easy to find, I'm not sure what would be a suitable choice for a speaker (or should I get two small speakers and hide them behind the speaker cloth and go stereo?). I'm totally open to advise and suggestions.

The unit is open back which I also have read can be a consideration when choosing speakers etc.

Does anyone have any input or guidance on where to start and what to look for? I don't mind spending a little bit of money, I'm not looking for anything more than something clean, clear and suitable for background music during the day.

Thanks for any help offered.

Cheers.

 

[thrifttrust]

That's a very cool looking radio. The dial portion seems perfect for a touch screen. The case, with it's open back and relatively light construction, limit how much power you can feed the speaker. You should be looking for a highly efficient speaker. To get the best bass with limited power you want the largest speaker that will fit in the opening. Efficient 8" full range speakers seem rare these days but this one from Parts Express seems well tailored to your project: Dayton Audio PS220-8 8" Point Source Full-Range Neo Driver. It's pricey but then quality large speakers tend to be.

Chipamp make a mono version of their amplifier: Non-Inverting LM3886 Mono Kit You have to assemble it and provide a heat sink. Check out the Chip amp subforum here at diyaudio. If you want a pre-assembled module there are fewer mono choices but there is no law that says you have to use both channels.

 

[29285]

for the small budget this one is a perfect choice
Visaton BG 20 - 8 Ohm Breitbandlautsprecher

 

[Ohkie]

That's a very cool looking radio. The dial portion seems perfect for a touch screen..

Thanks. Exactly what I was thinking when I saw it.

The case, with it's open back and relatively light construction, limit how much power you can feed the speaker. You should be looking for a highly efficient speaker. To get the best bass with limited power you want the largest speaker that will fit in the opening. Efficient 8" full range speakers seem rare these days but this one from Parts Express seems well tailored to your project: Dayton Audio PS220-8 8" Point Source Full-Range Neo Driver. It's pricey but then quality large speakers tend to be..

Thanks for the recommendation. To help someone as ignorant as I am out, can you explain to me which of the measurements on the diagram on parts express reflects the maximum diameter of the speaker? Is it 221.5 or 210? I'll need to figure out the maximum speaker width I can fit in the unit when I get home, and I fear the Dayton audio might be too big.

Chipamp make a mono version of their amplifier: Non-Inverting LM3886 Mono Kit You have to assemble it and provide a heat sink. Check out the Chip amp subforum here at diyaudio. If you want a pre-assembled module there are fewer mono choices but there is no law that says you have to use both channels.

I fear perhaps I've overcomplicated my plans. Are you saying that I can take a stereo amp, only connect one channel and leave the other unconnected? I thought I read somewhere this not safe for the hardware? I can use code on the raspberry pi to downmix stereo to a single channel, so if so that would be great.

I do like the idea of pre-assembled (it's daunting enough for me that I want to hook up some potentiometers and/or rotary encoders to the knobs) so I might go down that path.

 

[thrifttrust]

You're not ignorant. Dayton's drawing is simply wrong. I suspect the mounting hole circle is 210 and the speaker 221.5 overall. That's 8.7 inches. I guess 8 inch refers to the cone. Although the Dayton would work well it might be overkill. It was just the first best one I found at Parts Express. Inexpensive large speakers tend to be efficient. One like voltwide suggested should be fine. You just want one designed as a full range.

I can't think of a problem with leaving a dead channel. Ground the input, maybe put a load resistor on the output.

 

[Ohkie]

Thanks again. Starting to get a feel for this. Will look into some speaker options based on your recommendations.

One final question - if I purchased an assembled amplifier like the Dayton Audio da30 (for example) that does bridged mode, would that be a good fit for pairing with a single speaker?

Thanks for your help!

 

[afa]

You could use a single speaker designed for stereo, just do a search for "single stereo speaker", and for amplifiers you could use a class D amp Class D Amp: Amplifiers | eBay
cheers, Arthur.

 

[Ohkie]

I did see these single stereo speakers pop up - they mainly seem targeted at home theater ceiling installations. There's not a big range, and I'd be nervous about their suitability for putting in a 70 year old bakelite enclosure?

Will look into the suggested amps - thanks.

 

[thrifttrust]

You most definitely can use an amplifier that works in bridge mode for mono. I thought of suggesting it but didn't want to overly complicate the issue. The DA30 looks perfect.

 

[OffGridKindaGuy]

Would a driver like this work?

RetroSound D-52UK Dash Speaker Single 5-1/4" 2-way dash speaker with dual voice coils — stereo mix from a single speaker at Crutchfield.com